1. Field of the Invention
The present invention relates generally to a tool for working shaped, hollow metal tubing and, more particularly, to a tool for working shaped, hollow metal tubing to achieve an end reduction in the tubing.
2. Related Art
In the metal fabrication industry it is often necessary or advantageous to join adjacent lengths of hollow metal tubing to one another, as part of various structures. It is particularly advantageous to utilize either square or rectangular metal tubing in many applications, because of their shape and associated mechanical strength. Known methods of reducing square and rectangular metal tubing have typically utilized one or more dyes. With this form of reduction, one end of the square or rectangular tube is crushed by the force created by various configurations of press equipment, with the size of the reduction being determined by the die design. This method of end reduction of square and rectangular tubing is subject to the following disadvantages. In the first instance, the end reduction of the tubing may require several "hits" or applications of the press equipment to achieve the desired reduction, with each application adding to the manufacturing cost. Furthermore, the crushing force of the press equipment may cause excessive and/or non-uniform deformation of the tube end. More specifically, one or more of the sides of the tubing may become concave, thereby reducing the overall strength of the tube and detracting from the smoothness of the transition between the original shape and the reduced end. In certain instances, the excessive and/or non-uniform deformation may be so severe that the reduced end of the tube is not capable of insertion into a tube of the same size prior to reduction, as intended.
Due to the foregoing problems associated with the use of dies to end reduce square and rectangular tubing, connections of adjacent lengths of like-sized square and rectangular tubing are generally accomplished by inserting a smaller tube inside the two adjacent like-sized pieces of tubing, and then securing the joint by fastening each section of the outside tubing to the inside tube. The inside tube, as well as the required fasteners, add to the cost of this method of joining sections of square or rectangular tubing. Another disadvantage associated with this technique is that the strength of the joint is limited to the strength of the included fasteners.
In view of the foregoing disadvantages associated with known methods of connecting square and rectangular metal tubing, there is a continuing need for improved methods of joining adjacent sections of shaped metal tubing, such as square and rectangular tubing.